O2 adsorption on MO2 (M = Ru, Ir, Sn) films supported on rutile TiO2(1 1 0) by DFT calculations: Probing the nature of metal oxide-support interaction

Activity-Stability Trends of the Sb-SnO2@RuOx Heterostructure toward Acidic Water Oxidation

Accomplishments of enhanced activity and durability are a major concern in the design of catalysts for acidic water oxidation. To date, most studied supported metal catalysts undergo fast degradation in strongly acidic and oxidative environments due to improper controlling of the interface stability caused by their lattice mismatches. Here, we evaluate the activity-stability trends of in situ crystallized antimony-doped tin oxide (Sb-SnO₂)@RuO_x (Sb-SnO₂@RuO_x) heterostructure nanosheets (NSs) for acidic water oxidation. The catalyst prepared by atomic layer deposition of a conformal Ru film on antimony-doped tin sulfide (Sb-SnS₂) NSs followed by heat treatment highlights comparable activity but longer stability than that of the ex situ catalyst (where Ru was deposited on Sb-SnO₂ followed by heating). Air calcination for in situ crystallization allows the formation of hierarchical mesoporous Sb-SnO₂ NSs from as-prepared Sb-SnS₂ NSs and parallel in situ transformation from Ru to RuO_x, resulting in a compact heterostructure. The significance of this approach significantly resists corrosive dissolution, which is justified by the enhanced oxygen evolution reaction (OER) stability of the catalyst compared to most of the state-of-the-art ruthenium-based catalysts including Carbon@RuO_x (which shows ∼10 times higher dissolution) as well as Sb-SnO₂@Com. RuO_x and Com. RuO₂. This study demonstrates the controlled interface stability of heterostructure catalysts toward enhancing OER activity and stability.

Coaxial Nanofiber IrOx@SbSnOx as an Efficient Electrocatalyst for Proton Exchange Membrane Dehumidifier

Development of efficient catalysts for oxygen evolution reaction (OER) remains challenging in PEM dehumidifier or vapor electrolyzer. This study developed novel coaxial IrO_x@SbSnO_x nanofiber (NF) catalysts by electrospinning using a dual-channel needle. This method ensures the fibrous structure and the uniform loading of Ir oxide on the support of antimony tin oxide (ATO). IrO₂@SbSnO_x nanoparticles were synthesized for comparison. Characterizations showed that the active area and charge transfer resistance of NF was 1.47 times and 17.72% of that of commercial ones, respectively. The overpotential of NF at 10 mA·cm^-2 was 359 mV, much smaller than that of commercial IrO₂ (418 mV). In addition, the reaction overpotential of NF increased by only 38 mV after 1000 cyclic voltammetry cycles, indicating good electrochemical stability. To explore the enhancement mechanism, first-principles calculations were conducted for theoretically simulating the hetero-structures. Based on d-band theory, the structure formed between ATO and IrO₂ can effectively weaken the adsorption of oxygen intermediates on the catalyst surface, which reduces the OER energy barrier from 1.705 to 1.632 eV, causing an over 15% decrease of overpotential after loading on ATO. As a practical attempt, we applied the new catalysts in real PEM assembly for air dehumidification and found that the performance was improved by about 2 times compared with that using commercial catalysts. This study provides a research direction for the design of one-dimensional NF catalysts and their using in PEM applications.

Adsorption and dissociation of COCl2 on the rutile TiO2(110) surfaces: a systematic first-principles study

The adsorption and dissociation of phosgene (COCl₂) molecules on three kinds of rutile TiO₂(110) surfaces (stoichiometric: TiO₂-Sto; oxygen defective: TiO₂-Ov; and substoichiometric: TiO_1.875) were investigated based on density functional theory calculations. The nature of interactions between the COCl₂ molecule and rutile TiO₂(110) surfaces with different degrees of reduction was researched by the analysis of geometries, electron density difference, adsorption energies and density of states (DOS). Computational results show that COCl₂ indicates instability and will dissociate directly without the presence of transition states on a substoichiometric TiO_1.875(110) surface. The adsorption and dissociation behavior of COCl₂ on the rutile surface is not only helpful in providing theoretical support for the clean and efficient degradation of COCl₂, but also helpful in elucidating the role of COCl₂ as an intermediate product in the carbochlorination of titanium ore.

H2 adsorption and dissociation on PdO(101) films supported on rutile TiO2 (110) facet: elucidating the support effect by DFT calculations

To explore metal oxide-support interactions and their effect, H2 adsorption and dissociation on PdO(101)/TiO2(110) films with different film thicknesses, in comparison with that on pure PdO(101) surface without TiO2(110) support, were studied by density functional theory calculation. A monolayer PdO(101) film supported on TiO2 facet shows different properties to a pure PdO(101) surface. On the monolayer PdO(101)/TiO2(110) film, TiO2 support leads to stronger molecular adsorption of H2 on coordinatively unsaturated Pd top sites than that on a pure PdO surface. H2 dissociation with the formation of OH was preferred thermodynamically but slightly unfavorable kinetically on the monolayer PdO film due to the TiO2 support effect. Graphical abstract On the monolayer PdO(101)/TiO2(110) film, the TiO2 support effect leads to stronger H2 molecular adsorption on coordinatively unsaturated Pd top sites than on pure PdO surface. H2 dissociation with the formation of OH is preferred thermodynamically but slightly unfavorable kinetically on the film due to the TiO2 support effect.